Beverages containing deamidized gluten

ABSTRACT

Native gluten is subjected to successive extractions with anhydrous isopropanol, aqueous alkali isopropanol, and aqueous acidic isopropanol to remove astringent principles. The gluten is then hydrolyzed with dilute acid to convert amide groups to carboxy groups. The non-astringent deamidized gluten is incorporated in beverages including acidic beverages such as fruit juices.

United States Patent Finley Nov. 6, 1973 [54] BEVERAGES CONTAININGDEAMIDIZED 3,030,211 4/1962 McDonald 99/14 GLUTEN 2,567,980 9/1951 Tuomyet al 260/112 6 75 l J h w F l M c If 3,713,843 1/1973 Pour-Elet al99/28 x 1 l 1 M 0 n ey armez FOREIGN PATENTS OR APPLICATIONS [73]Assgneel The Umted as 708,806 5/1954 Great Britain 99 14 represented bythe Secretary of Agnculture washmgton' Primary ExaminerMorris O. Wolk 22l May 3 1972 Assistant ExaminerStephen B. Davis Att0rneyR. Hoffman eta1. 21 Appl. No.: 251,166

[57] ABSTRACT [52] US. Cl 426/190, 99/14, 99/17, Native gluten issubjected to successive extractions 99/105, 260/112 G with anhydrousisopropanol, aqueous alkali isopropa- [51] Int. Cl. A231 l/00, A23j 1/12nol, and aqueous acidic isopropanol to remove astrin- [58] Field ofSearch 99/28, 14, 17, 105; gent principles. The gluten is thenhydrolyzed with di- 260/112 G lute acid to convert amide groups tocarboxy groups. The non-astringent deamidized gluten is incorporated[56] References Cited in beverages including acidic beverages such asfruit UNITED STATES PATENTS j 2,420,735 5/1947 Coffman et a1. 260/117 G5 Claims, No Drawings BEVERAGES CONTAINING DEAMIDIZED GLUTEN Anon-exclusive, irrevocable, royalty-free license in the invention hereindescribed, throughout the world for all purposes of the United StatesGovernment, with the power to grant sublicenses for such purposes, ishereby granted to the Government of the United States of America.

DESCRIPTION OF THE INVENTION source of protein and readily obtainablefrom cerealgrains, has been considered as an additive for this purpose.Unfortunately, gluten is not compatible with the acidic aqueous mediathat make up such beverages. If unmodified (native) gluten is added toan acidic beverage, a cloudy suspension forms. Very little, if any, of

the gluten is dissolved. As a result, the appearance of the beverage isimpaired and when imbibed has an undesirable effect on the palatebecause of its gritty texture. Also, if the beverage is allowed tosettle and only the clear liquid imbibed, the consumer will obtain noneof the benefit of the added protein. Another'item to be considered isthat native gluten develops undesirable astringency when contacted withan acidic aqueous medium such as an acidic beverage. The taste sensationis developed far back in the mouth and is described by some as athroat-burning, puckering, or bitter sensa tion.

The primary object of the invention is to obviate the problems. outlinedabove. In accordance with the invention, gluten is deamidized so that itis soluble in acidic aqueous media. As a result, the modified(deamidized) gluten can be effectively employed for the nutritionalfortification of beverages of all kinds, including those of an acidnature such as carbonated and non-carbonated soft drinks, simulatedfruit juices, authentic fruit juices, etc. Also in accordance with theinvention, the native gluten is subjected to a treatment to remove theastringent principles, whereby the modified gluten of the invention doesnot impair the taste of the beverage to which it is added.

DETAILED DESCRIPTION As the starting material for the practice of theinvention one may use gluten obtained from any cereal source. Apreferred starting material is vital gluten which contains approximately50 percent gliadin and 50 percent glutenin. It is prepared by making adough of wheat flour and water and kneading the dough while washing itwith water to remove the starch. The resulting wet gluten is then driedat a relatively low temperature to prevent degradation of the proteinmolecules. The product is referred to as vital because it is notdenatured during its preparation.

In a first operation in accordance with the invention, vital gluten isextracted with anhydrous isopropanol to remove the astringentprinciples. For optimum results, a series of extractions are applied:First the gluten is extracted with anhydrous isopropanol. This initialextraction is followed by another iii which 0.05 to 0.1 N foodgradealkali (e.g., NaOI-I or KOI-I) in 5-10 percent aqueous isopropanol isused as the solvent. Following this, the gluten is extracted with 0.05to 0.1 N foodgrade acid (e.g., hydrochloric or sulphuric) in 5-10percent aqueous isopropanol to neutralize the gluten. It is, of course,obvious that the extractions may be repeated a number of times to ensurecomplete removal of astringent principles. Ambient. temperatures orlower (e.g., 25 down to about minus 15 C.) are employed to minimizedenaturation of the gluten by the applied agents. Following eachextraction the solid gluten can be separated from the liquid byconventional means such as decanting, filtering, or centrifuging.Generally, in each extraction a 5-20 to 1 ratio (volume to weight) ofextraction solvent to gluten is employed. It may be observed that thisextraction procedure does not alter the proteinous components of thegluten since both gliadin and glutenin are insoluble in the statedsolvents. Gliadin, for example, is not soluble in anhydrous isopropanolor that containing 10 percent water; it is only soluble in isopropanolcontaining at least 20 percent of water.

Following the removal of astringent principles, the

gluten is deamidized by very dilute acid hydrolysis under controlledconditions. In this hydrolysis the primary amide groups (-CONH occurringalong the protein chains are hydrolyzed to carboxyl groups (-COOI-I)without significant rupturing of the peptide linkages which form theprotein chains. Methods of preparing deamidized gluten are known in theart and form no part, per se, of the present invention. It is evidentthat by changing the conditions of hydrolysis, one may vary theproportion of amide groups which are converted into carboxy groups. Forpurposes of the invention, we use deamidized glutens wherein at least 20percent of the amide groups are converted into carboxy groups. Formaximum dispersibility in acidic beverages, it is preferred to employthe products in which about 45 to percent of the amide groups areconverted into carboxy groups. I

Generally, 0.05 to 1.0 N HCl is used for the deamida tion and is appliedat a temperature from 25 to C. for a period of about 20 minutes to 24hours. As mentioned earlier, the extent of deamidation can be controlledby varying the above conditions of hydroly- SIS.

After the hydrolysis the deamidized gluten is dried in conventionalmanner, for example, spray or freeze drying. The dried material is readyfor use as a beverage fortifier. Since the solid has a powdery nature,it is excellent for fortification because it allows a specific amount tobe metered out for a particular liquid food or beverage. The powder isfree-flowing and easy to handle and readily dissolves in eitherdistilled water or water at pH 2-7.

It is to be particularly observed that deamidized gluten offersconsiderable advantages-important in the preparation of food productsascompared with unmodified gluten.

Unmodified gluten is sensitive to heat. Thus, if it is used in beverageswhich are subjected to heatas for pasteurizing or sterilizing duringbottling or canning-deterioration of the gluten occurs which renders itnutritionally useless. Deamidized gluten, on the other hand, is notsensitive to heat and may be used with equal success in cold and hotbeverages and in those which are subjected to thermal processes such aspasteurization or sterilization.

Unmodified gluten is sensitive tp pH and is insoluble or only slightlysoluble at pH 2 to 7. This means that the protein cannot be used inbeverages having such a pH range. On the other hand, deamidized glutenis soluble over this entire pH range and thus can be used in suchproducts.

The invention is of wide versatility and may be utilized for thenutritional fortification of all kinds of beverages, for example:

Carbonated beverages such as colas, ginger ale, root beer, cream soda,and the various fruit-flavored sodas such as grape, lemon and lime,orange, cherry, etc.

Non-carbonted beverages including fruit-flavored drinks such as orange,lemon, lime, grape, grapefruit, cherry, etc.

Fruit juices including orange, apple, pineapple, grapefruit, etc., andsimulated juices which contain some proportion of fruit juice plus addedsugar, flavorings, citric acid, etc.

Vegetable juices such as tomato juice, carrot juice, celery juice, andmixtures of tomato juice with other vegetable juices.

Beverage bases such as the dry products which contain sugar (orartificial sweetener), fruit flavor (real or imitation), citric or otherfruit acid, and coloring.

Coffee and tea, both in liquid and dehydrated forms. Wines, beer, ale,and the like.

In a practice of the invention, deamidized gluten is incorporated in thebeverage in a desired proportion. Thus, the amount added is not criticalbut merely depends on the degree of nutrient enhancement desired.Usually, we add at least 1 percent, preferably at least 3 percent. Ifdesired, the proportion may be as high as or percent. Although theinvention is particularly adapted for the nutritive fortification ofacidic beverages it can be applied to any beverages and to other liquidfoods such as whole milk, skim milk, soups, sauces, gravies, and thelike.

In US. Pat. No. 3,030,211 there are described certain food productscontaining added deamidized gliadin. Although this patent (hereinafterreferred to as US. Pat. No. 3,030,211) describes a procedure ofdeamidation similar to that described herein, the two inventions arequite distinct. In the first place, US. Pat. No. 3,030,211 is concernedwith deamidized gliadin, not deamidized gluten. The procedure of US.Pat. No. 3,030,21 l precludes its application to gluten since specialtechniques are used to extract gliadin therefrom. In the presentinvention the deamidized gluten product contains its natural complementof both gliadin and glutenin.

Secondly, the deamidized gliadin in US. Pat. No. 3,030,211 is employedas a stabilizer in food products such as cake frostings, desserttoppings, candies, meringues, and the like, which are subject to leakageof watery serum, graininess, and loss of volume. There is no disclosurein US. Pat. No. 3,030,21 1 of incorporating deamidized gliadin intoacidic beverages, and there is no suggestion that this substance wouldbe compatible with such beverages.

Also, a feature of the present invention is that the native gluten issubjected to a treatment to remove astringent principles. The patent inquestion discloses no such step. Rather, the astringent principlesremain in the deamidized gliadin, but are masked by the sweetness of theproducts into which it is incorporated.

EXAMPLES The invention is further demonstrated by the followingillustrative examples.

EXAMPLE 1 Vital gluten (30 g.) was successively extracted with thesolvents listed below, applying centrifugation after each extraction toseparate the solvent from the treated gluten. The extractions wereconducted at minus 15 C.

Anhydrous isopropanol (500 ml.).

Two 500-ml. portions of 0.1 N NaOH in 10 percent aqueous isopropanol.

500 ml. of 0.1 N hydrochloric acid in 10 percent aqueous isopropanol.

The so-treated gluten was then hydrolyzed (deamidized) with 1.4 litersof 0.075 N HCl in a steam-heated mixing bowl for 30 minutes. Temperatureof the hydrolysis mixture was about C. Following this, the mixture waslyophilized to remove the liquid components.

The resulting dry, non-astringent, deamidized gluten was found to becompletely soluble in pH 3 citrate buffer. Its flavor was bland; theastringent taste of the original gluten was totally absent.

EXAMPLE 2 Dry non-astringent deamidized gluten prepared as described inExample 1 was incorporated in the proportion of 3 percent in a series ofacidic beverages, namely, orange juice, lemon juice, lemonade,grapefruit juice, pineapple juice, pineapple-orange juice, andpineapple-grapefruit juice. It was observed that in each case themodified gluten went into solution, and each of the beverages exhibitedthe same flavor and texture as the corresponding unfortified one.

Having thus described my invention, I claim:

1. A process for preparing non-astringent deamidized gluten whichretains its natural content of both gliadin and glutenin, whichcomprises a. successively extracting vital gluten withessentiallyanhydrous isopropanol, 0.05 to 0.1 N food-grade alkali in5-10 percent aqueous isopropanol, and 0.05 to 0.1 N food-grade acid in5-10 percent aqueous isopropanol, and

b. hydrolyzing the so-extracted gluten with dilute acid to convert amidegroups to carboxy groups without rupturing the protein chains of thegluten.

2. In the process for preparing deamidized gluten wherein native glutenis hydrolyzed with dilute acid to convert amide groups to carboxygroups, the improvement which comprises subjecting the native glutenprior to the hydrolysis to successive extraction with a. essentiallyanhydrous .isopropanol b. 0.05 to 0.1 N food-grade alkali in 5-10percent aqueous isopropanol, and c. 0.05 toO.1 N food-grade acid in 5-10percent aqueous isopropanol. 3. A beverage containing non-astringentdeamidized gluten produced according to the process of claim 2 acidicbeverage, which comprises dissolving therein about 1-15 percent ofnon-astringent deamidized gluten produced according to the process ofclaim 2 which contains its natural content of both gliadin and glutenin.

2. In the process for preparing deamidized gluten wherein native glutenis hydrolyzed with dilute acid to convert amide groups to carboxygroups, the improvement which comprises subjecting the native glutenprior to the hydrolysis to successive extraction with -a. essentiallyanhydrous isopropanol b. 0.05 to 0.1 N food-grade alkali in 5-10 percentaqueous isopropanol, and c. 0.05 to0.1 N food-grade acid in 5-10 percentaqueous isopropanol.
 3. A beverage containing non-astringent deamidizedgluten produced according to the process of claim 2 which contains itsnatural content of both gliadin and glutenin.
 4. An acidic beveragecontaining in solution at least 1 percent of non-astringent deamidizedgluten produced according to the process of claim 2 which contains itsnatural content of both gliadin and glutenin.
 5. A process for enhancingthe nutritive value of an acidic beverage, which comprises dissolvingtherein about 1-15 percent of non-astringent deamidized gluten producedaccording to the process of claim 2 which contains its natural contentof both gliadin and glutenin.